A number of investigations have focused on attempting to identify endogenous hormones related to risk of a variety of tumors, including breast, endometrial and prostate cancers. Relationships with breast cancer diseases (including cancer) have been pursued using data from the Mayo Serum Bank as well as a case-control study among Asian-American women. Further follow-up of participants in the Columbia, Missouri component of the Mayo Serum Bank is being pursued to expand upon previous findings and to enable additional hypotheses to be addressed. Within these studies, attention has focused not only on classically accepted predictors, but also some more newly suggested hormones, including insulin-like and other growth factors. Our research has also attempted to advance our understanding of predictors of endogenous hormones. This has included analyses within the control populations of several case-control studies, as well as a hormone ancillary study to evaluate the effect of diet intervention (specifically fat modification aimed at lowering low density lipoprotein cholesterol) on serum sex hormone concentrations. Further follow-up among a cohort of women screened for bone density is being planned to better understand how this relates to subsequent risk of breast, endometrial and other cancers. Efforts are also underway to assess how hormone levels are influenced by a variety of genetic factors, including several hormone metabolizing genes. Efforts are also being made to better understand the functionality of these genes, including effects on endogenous hormones. Findings that physical activity can affect endogenous hormones levels have prompted our interest in evaluating relationships with several hormonally-related cancers. Special efforts have been expended on improving exposure assessment. In an ongoing study in Poland, accelerometers are being used to obtain more objective measures than interview data alone. Reasons for the geographic variation in breast cancer have been explored in several investigations. As one possible explanation, there has been a focus on effects of organochlorines, which were not found related to risk in one investigation. Studies are also exploring relationships with other sites, including endometrial, ovarian and testicular cancers. Effects on breast cancer have also been explored in relation to alcohol ingestion, cigarette smoking and use of electric blankets, but none were associated with any substantial alterations in risk. The rising incidence of prostate cancer in China led to initation of a multidisciplinary case-control study in Shanghai. Body size has been found to be a major predictor of risk; current analyses are focusing on relationships with calories, consumption of red meat, fatty acids and endogenous hormones. A methodologic study has also been initiated to assess how serum hormones relate to intraprostatic levels. - Human Subjects & Human Subjects: Interview, Questionaires, or Surveys Only & Human Tissues, Fluids, Cells, etc.